Method of lubricating bearings



United States Patent METHOD OF LUBRICATING BEARINGS Application December 19, 1955 SerialNo. 553,688

4 Claims. (31. 2s2 32.7)

'No Drawing.

This invention relates to lubricating grease compositions, and especially to water-resistant lubricating greases which have outstanding high and low temperature properties. More particularly, the invention relates to lubricating grease compositions which have high dropping points, good Water resistance and excellent extreme pressure properties. It relates, moreover, to lubricating grease compositions which are prepared by thickening lubricating oil to a grease consistency with a new type of thickener in the form of the metal salts of the reaction product of a sulfideof phosphorus and a suitable hydrocarbon material.

This application is a continuation-in-part of Serial No. 299,004, filed July 15, 1952, now abandoned.

It has now been found that the metal salts of the reaction product of sulfides of phosphorus and suitable hydrocarbon materials will act as grease-thickening agents for lubricating oils. In addition to thickening the lubricating oil'to a grease consistency, these metal salts impart other desirable properties to the grease compositions. For example, extreme pressure chracteristics result from the incorporation of phosphorus and sulfur-containing materials. Furthermore, the grease compositions of the invention have high dropping points and excellent resistance to water.

The lubricating oil used as the dispersant for the above thickening agents may be any of the commonly known lubricating oils, either naturally occurring or synthetic. Mineral lubricating oils, suitably refined, having viscosities ranging from about 40 to 1000 or more Saybolt seconds Universal, at 100 F. are operable. It is preferred to use as a mineral oil base, a distillate having a viscosity at 100 F. within a range of fiom about 50 S. U. S. to about 400 S. U. S.

Any of the commonly known synthetic lubricating oils may also be used as the dispersant or a part thereof. Esters of dibasic acids having from 4 to carbon atoms in the ester group, such as C C alcohol esters of glutaric, adipic, pimelic, suberic, azelaic or sebacic acid, and the like, may be used. Complex esters of the type alcoholdibasic acid-glycol-dibasic acid-alcohol represented, for example, by the formula:

ester, according to the above formula, is formed by reacting two mols of the 2-ethylhexanol half ester of adipic acid with one mol of a polyethylene or polypropylene glycol having a molecular weight of about 200. Other synthetic lubricants such as polymerized silicones, polymerized olefins, polyglycols, polyglycerol, glycol esters, glycol ethers, glycol ether esters, alkylated aromatics, carbonates, formals, etc. may serve as the lubricating oil base or dispersant for the lubricating grease compositions of the invention.

2,859,178 Patented Nov. 4, 1958 The thickening agent for these novel greases may be broadly described as the metal salts of the reaction prodnot of a sulfide of phosphorus with a hydrocarbon. The treatment of various hydrocarbons with sulfides of phosphorus such as P 8 andP S and their homologues is well known in the art, and such treatment forms no part of the concept of this invention. However, the discovery that the metal salts of these reaction products may serve as thickeners for the preparation of high quality grease compositions having certain exceptional properties is believed to be novel. Proportions varying from 22 to 60% by weight of the metal salts of the phosphorus sulfide treated hydrocarbon, based on the total grease composition, are utilized as the thickening agent in order to attain solid solid stable grease compositions. A preferred range of thickener is between about 24 to 55% by weight, based on the weight of the total grease composition.

In general, the hydrocarbons that are most suitable for the treatment with the sulfide of phosphorus are those of higher molecular Weight such as lubricating oil fractions, particularly bright stocks and related lubricating oil residues; high molecular weight olefins such as dicyclopentadiene; olefin polymers derived from materials of lower molecular weight such as polyisobutylene and polypropylene; synthetic hydrocarbon oils obtained by alkylation of olefins with or Without polymerization, etc. alkylated aromatics, alkylated naphthenes and the like. Hydrocarbon residues having a viscosity from 35 to 10,000 or more S. S; U. at F. are preferred.

Metallic bases useful in the reaction with the phosphorus sulfide treated hydrocarbons include alkali metals such as sodium and lithuim; alkaline earth metals such as calcium, barium and strontium; and metals of groups III and IV'of the periodic table such as aluminum and lead.

Although the hydrocarbon material chosen may be treated with the sulfide of phosphorus in many ways, it is preferred in the instant invention to treat the hydrocarbon with from 10% by weight to 20% by weight of the phosphorus sulfide, based on the weight of the hydrocarbon, at temperatures ranging from about 300 F. to 500 F. for from about 4 to 15 hours or more. By utilizing these preferred reaction conditions, appreciable percentages of sulfur and/ or phosphorus are incorporated into the reaction product.

The invention will be more fully understood by reference to the following specific examples illustrating various modifications of the invention.

EXAMPLE I Composition A A Mid-Continent'bn'ght stock having a viscosity at 210 F. of S. U. S. was treated with 17 weight percent of P 5 at a temperature of about 400 F. for 10 hours. The reaction product was filtered, diluted with a mineral oil distillate having a viscosity at 210 F. of 40 S. U. S. The mixture was then neutralized with 30% by weight of barium hydroxide octahydrate, based on the weight of the P S -treated hydrocarbon. The final composition, after incorporation of the mineral oil and cooling to room temperature,.contained 15% by weight of the barium salt of the P S -treated hydrocarbon. and 85% by weight of mineral oil. p j

Compositions B, C, D and E These compositions were prepared similarly to Composition A except that the amount of mineral oil added was controlled to obtain compositions containing 18%, 247;, 30% and 36% by weight of the barium salt, respective y.

Various inspections of the above compositions are set forth below:

'The above'data show that solid lubricating grease compositions having high dropping points and excellent water resistance were obtained by employing at least 24 wt. percentof the barium salt'of the reaction product of P S and bright stock (Compositions C, D and E). Where the amount of barium salt employed was less than 24 wt.'percent.(Compositions A and B) the resulting products were either fluid or semi-fluid on working. It will be particularly noted that Composition 3 had a worked penetration of about 387, which characterizes it as a semi-fluid composition. See pages 3034 of Lubrication of Industrial-and Marine Machinery, by William G. Forbes (John Wiley & Sons, Inc., New'York), wherein the'jcorrelation between worked penetrations and the physical description of greases at room temperature is given. T a

Y 'EXAMPLE 11 Using the procedure of Example I, a grease composition Dropping point 285 F. Penetration, unworked 105 mm./l 77 F. Penetration, worked (60 strokes,

fine hole Worker plate) 182 mm./l0 77 F. Nater resistance (30 min. I

210 F.) Good, some clouding; BEC test 1 Good lubrication.

1 The BEC test consists of operating a standard 'ball bearing.

for 20 minutes at various temperatures, using the test grease for lubrication. After the duration of the test, the-bearin is examined for loss of grease, slumping 1n the bearing, an

oil separation.

EXAMPLE I11 Another lubricating grease composition was prepared in accordance with the invention by the procedure described in Example I above. In this instance, however, calcium hydroxide was used instead of barium hydroxide to neutralize the P S -treated hydrocarbon. Oil was added before neutralization as in Example L The final composition of the sample was 45% by weight of the calcium salt and 55% by weight of the mineral oil. The

product solidified toa grease, and it had the following inspections:

Dropping point 500 F.

Penetration, unworked 140 mm./ 77 .F.

Penetration, worked (60 strokes, finehole worker plate) 177 mm./ 10 77 F.

Water resistance (30 min. 1

210 F.) Excellentno clouding.

4 e The data obtained in connection with the examples given above show that grease compositions made accord-i ing to this invention were outstanding lubricants, having dropping points, good structural stability and excellent,

water resistance.

To summarize briefly, it will be seen that this invention relates to novel lubricating grease compositions, which are prepared by thickening a lubricating oil to grease consistency with metal salts of the reaction'prodnets of sulfides of phosphorus with a hydrocarbon mate rial. In the preferred embodiment of the'invention, a P S -treated bright stock is used to form the metal salt with metal exemplified by sodium, lithium, calcium, barium, strontium, aluminum and lead. Other metal bases such as zinc, iron, etc., also appear to have utility for some purposes. The alkali and alkaline earth metal bases are particularly preferred.

.The invention is not limited to the, specific conditions and materials of the foregoing examples. These conditions and materials may be varied within the limits indicated in the general portions of the specification; Furthermore, it will be understood that various conventional additives may be used singly or in combination in; the new greases Without departing from the spirit or pur-; pose of the invention. 'Ihus, anti-oxidants, tackiness; agents, extreme pressure additives, metal deactivators, rust inhibitors, oil thickeners, viscosity index improvers etc. may be used. Minor proportions of soap or non: soap thickeners may also be used along with'the salts of tP s -hydrocarbon reaction productsas supplementary thickening or solidifying agents. Inorganic thickeners'or fillers suchas carbon black, silica, silica gel, bentonite,

mica, etc., may be added as in other types of greases.

known tothe art. g 7 p "'What isclaimedist a 1. A method of lubricating bearings which comprises maintaining on said bearings a film of a water resistant and structurally stable lubricating grease composition? comprising a lubricating oil and a grease thickenin'g amount with in the range of about 22 to wt. percent}; based on the total composition, of a-greasethickeiiergl said grease thickener being a metal salt of the'reactioni productof a high molecular weight hydrocarbon reacted with about 10 to 20 wtpercent of a phosphorus at a temperature of about 300 to 500 F. for about 31ft 15 hours, said metal being selected from the group 'co sisting of sodium, lithium, calcium, barium, strontium,,. .j aluminum and lead. p

2,. The method of claim 1 wherein said lubricatingl'o.

base is a'mineral lubricatingoih V I .r

3. The method of claim 1 wherein said sulfide of phos l phorus is P S 4. The method of claim 1 wherein said hydrocarbon residue is brightstoek.

7 References Cited inthe file of this patent UNITED STATES- PATENTS Re. 23,676 Bartleson 'Iune :30, 1953 2,316,079 Loane et al. 'A pr. 6, 1943" 2,316,085 Kelso et al Apr. 6, 1943 2,507,731 Mixon et al May 16, 1950 2,688,612 Watson Sept. 7, 1954 

1. A METHOD OF LUBRICATING BEARINGS WHICH COMPRISES MAINTAINING ON SAID BEARINGS A FILM OF A WATER RESISTANT AND STRUCTURALLY STABLE LUBRICATING GREASE COMPOSITION COMPRISING A LUBRICATING OIL AND GREASE THICKENING AMOUNT WITH IN THE RANGE OF ABOUT 22 TO 60 WT. PERCENT, BASED ON THE TOTAL COMPOSITION, OF A GREASE THICKENER, SAID GREASE THICKENER BEING A METAL SALT OF THE REACTION PRODUCT OF A HIGH MOLECULAR WEIGHT HYDROCARBON REACTED WITH ABOUT 10 TO 20 WT. PERCENT OF A PHOSPHORUS SULFIDE AT A TEMPERATURE OF ABOUT 300 TO 500*F. FOR ABOUT 4 TO 15 HOURS, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF SODIUM, LITHIU,, CALCIUM, BARIUM, STRONTIUM, ALUMINUM AND LEAD. 